Cyclopeptide alkaloids from Scutia buxifolia Reiss

Scutianene E (1), 3,4,28-tris-epi-scutiaene E (2), 28-epi-scutianene E (3) and scutianene L (4), four neutral cyclopeptide alkaloids, were isolated from Scutia buxifolia Reiss, together with four known cyclopeptide alkaloids, scutianines B, C, D and E. Scutianenes 1-3 are diastereoisomeric compounds, with 3-hydroxyleucine as a β-hydroxy amino acid unit, which is connected to the styryl fragment via an ether bridge, β-phenylserine, as a common ring-bonded amino acid residue. Attached to the amino group of β-hydroxyamino acid is a side chain [trans-CH = CH-Ph]. The structures of the peptides were elucidated by means of spectroscopic analysis, including extensive 2D NMR studies. The stereochemistry for the diastereomeric 3,4,28-tris-epi-scutiaene E and 28-epi-scutianene E was confirmed by X-ray diffraction analysis of their O-acetyl derivatives.     

Structure-Activity Relationship of Benzophenanthridine Alkaloids from Zanthoxylum rhoifolium Having Antimicrobial Activity

Zanthoxylum rhoifolium (Rutaceae) is a plant alkaloid that grows in South America and has been used in Brazilian traditional medicine for the treatment of different health problems. The present study was designed to evaluate the antimicrobial activity of the steam bark crude methanol extract, fractions, and pure alkaloids of Z. rhoifolium. Its stem bark extracts exhibited a broad spectrum of antimicrobial activity, ranging from 12.5 to 100 µg/mL using bioautography method, and from 125 to 500 µg/mL in the microdilution bioassay. From the dichloromethane basic fraction, three furoquinoline alkaloids (1–3), and nine benzophenanthridine alkaloids (4–12) were isolated and the antimicrobial activity of the benzophenanthridine alkaloids is discussed in terms of structure-activity relationships. The alkaloid with the widest spectrum of activity was chelerythrine (10), followed by avicine (12) and dihydrochelerythrine (4). The minimal inhibitory concentrations of chelerythrine, of 1.50 µg/mL for all bacteria tested, and between 3.12 and 6.25 µg/mL for the yeast tested, show this compound to be a more powerful antimicrobial agent when compared with the other active alkaloids isolated from Z. rhoifolium. To verify the potential importance of the methylenedioxy group (ring A) of these alkaloids, chelerythrine was selected to represent the remainder of the benzophenanthridine alkaloids isolated in this work and was subjected to a demethylation reaction giving derivative 14. Compared to chelerythrine, the derivative (14) was less active against the tested bacteria and fungi. Kinetic measurements of the bacteriolytic activities of chelerythrine against the bacteria Bacillus subtilis (Gram-positive) and Escherichia coli (Gram-negative) were determined by optical density based on real time assay, suggesting that its mechanism of action is not bacteriolytic. The present study did not detect hemolytic effects of chelerythrine on erythrocytes and found a protective effect considering the decrease in TBARS and AOPP (advanced oxidized protein products) levels when compared to the control group.     

Cyclic peptide alkaloids from the bark of Discaria americana

The isolation and structure determination of cyclic peptide alkaloids, discarine-M and discarine-N, along with seven known cyclic peptide alkaloids, adouetine-Y', franganine, frangulanine, discarines-A, -B, -C, and -D from the root bark of Discaria americana are described. Structures were determined spectroscopically, especially using 2D NMR spectroscopic analysis. The crude methanol extract, the basic ether extract, and the alkaloids 6 and 7 also weakly inhibited growth of gram-negative and gram-positive bacteria.     

An unusual quinolinone alkaloid from Waltheria douradinha

The chemical investigation of the methanolic extract of the root bark of Waltheria douradinha (Sterculiaceae) afforded an unusual quinolinone alkaloid named waltherione-A (1). Its structure was determined mainly by NMR spectroscopic methods. The antibacterial activity of waltherione-A (1) and the corresponding O-methylated derivative (2) was tested against three gram-negative and three gram-positive bacteria, with only (2) having moderate activity.     

Cyclopeptide alkaloids from Scutia buxifolia Reiss and their antimicrobial activity

The present study reports a cyclopeptide alkaloid, scutianine M, isolated from the methanolic root bark extract of Scutia buxifolia Reiss (Rhamnaceae) along with six known compounds, scutianines-B, -C, -D, -E, -F, and scutianene D. Its structure was established on the basis of spectroscopic analyses, including application of 2D NMR spectroscopic techniques. As part of a study of the bioactive compounds of medicinal plants from southern Brazil, we also compared the antimicrobial activity of the isolated compounds towards Gram (+), Gram (-) bacteria, and yeasts.     

Self-assembly of the amphipathic helix (VHLPPP)8. A mechanism for zein protein body formation

gamma-Zein, a maize storage protein with an N-terminal proline-rich repetitive domain (gamma-ZNPRD), is located at the periphery of protein bodies. This domain appears to be indispensable for the aggregation of the protein on the surface of the organelle. The peptide (VHLPPP)8, spanning the gamma-ZNPRD, adopts a polyproline II (PPII) conformation that gives an amphipathic helix different from the alpha-helix. We used atomic force microscopy to study the surface organisation of the octamer, and transmission electron microscopy to visualise aggregates of the peptide in aqueous solution. We consider two self-assembly patterns that take account of the observed features. The micellar one fits best with the experimental results presented. Moreover, we found that this peptide has properties associated with surfactants, and form micelles in solution. This spontaneous amphipathic arrangement of the gamma-ZNPRD suggests a mechanism of gamma-zein deposition inside maize protein bodies.     

Supramolecular properties of the proline-rich gamma-Zein N-terminal domain

Zeins are maize storages proteins that accumulate inside large vesicles called protein bodies. gamma-Zein lines the inner face of the protein body membrane, and its N-terminal proline-rich repetitive domain with the sequence (VHLPPP)(8) appears to be necessary for the accumulation of the protein within the organelle. Synthetic (VHLPPP)(8) adopts an amphipathic polyproline II conformation. In a preliminary recent work we used atomic force microscopy to study the surface organization of the octamer and transmission electron microscopy to visualize aggregates of the peptide from aqueous solution. We previously envisioned two self-assembly models (i.e., the geometric and the micellar) that take into account the observed features. In the present work we studied in detail the self-assembly of the peptide in solution and found that the peptide is able to form cylindrical micelles. Fibrils formed on graphite are generated by assembly of solution micelles. Based on the results of these studies, we focused exclusively on the micellar model. To our knowledge we have characterized for the first time supramolecular aggregates of polyproline structures other than collagen. The spontaneous arrangement of (VHLPPP)(8) suggests a role for the N-terminal domain of gamma-zein in the process of the whole protein deposition in protein bodies.     

Manufacturing Flexibility: Assessing Managerial Perception and Utilization

This paper presents an empirical study of how consumer electronics companies in Brazil deal with the issue of manufacturing flexibility. The main purpose is to provide an understanding into how flexibility is being perceived and utilized in a newly industrialized country. It begins by explaining the relevance of this study. The participation of Brazil in the world economy is important. Here, companies can be very flexible, based on low cost and an abundant skilled work force, yet flexibility has not been addressed. The paper explains how indicators were established to obtain an analytical structure with which to assess the managerial perception and the actual industrial use of flexibility. Finally, we show the most relevant results of our investigation of 16 leading firms in Brazil, including multinational ones. The findings are divided according to managerial perception of flexibility and effective utilization of flexibility in the organization. The paper concludes that firms in the consumer electronics industry in Brazil do not use flexibility practices in the same proportion that they perceive its importance.     

Quinolone alkaloids from Waltheria douradinha

A phytochemical investigation of the stems of Waltheria douradinha resulted in isolation of two 4-quinolone alkaloids, waltherione B and vanessine, along with three known alkaloids, waltherione A, antidesmone and O-methyltembamide. Their structures were elucidated on the basis of their 2D NMR spectroscopic analyses, and from X-ray crystallographic analysis of waltherione A and the O-methyl derivative of waltherione B. Additionally, waltherione B and vanessine, and the O- and N-methyl derivatives of waltherione A and waltherione B, were evaluated for their antimicrobial activities; only vanessine displayed any (weak) antimicrobial activity.